gerlowskija opened a new pull request, #4189: URL: https://github.com/apache/solr/pull/4189
https://issues.apache.org/jira/browse/SOLR-18146 # Description A previous improvement (SOLR-17761) switched the class over to using ConcurrentHashMap for its global CBs, but each map entry itself was still an ArrayList, which are not thread-safe for modifications. With sufficiently unlucky timing, this could lead to "ArrayIndexOutOfBoundsExceptions" during the core-load phase of Solr startup. # Solution This commit fixes this problem in two ways: 1. It replaces the vanilla ArrayList with a CopyOnWriteArrayList, which are safer for concurrent modification. 2. It puts synchronization around the global CB loading itself, to ensure that it's run by one (and only one) thread at a time. The first thread to aquire the lock will load the global CBs. Subsequent threads will notice that the CBs have already been loaded and skip any attempt to modify those data structures. # Tests This PR contains a 'TestConcurrentCircuitBreakerRegistration' which I used to reproduce the race condition. I'm not sure if it's worth committing or not. (Claude helped write this test) # Checklist Please review the following and check all that apply: - [x] I have reviewed the guidelines for [How to Contribute](https://github.com/apache/solr/blob/main/CONTRIBUTING.md) and my code conforms to the standards described there to the best of my ability. - [x] I have created a Jira issue and added the issue ID to my pull request title. - [x] I have given Solr maintainers [access](https://help.github.com/en/articles/allowing-changes-to-a-pull-request-branch-created-from-a-fork) to contribute to my PR branch. (optional but recommended, not available for branches on forks living under an organisation) - [x] I have developed this patch against the `main` branch. - [x] I have run `./gradlew check`. - [x] I have added tests for my changes. - [ ] I have added a [changelog entry](https://github.com/apache/solr/blob/main/dev-docs/changelog.adoc) for my change -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
